Televisions and other types of imaging systems are pervasive in today's society. Recent years have seen the introduction of higher definition imaging systems. Engineers continue to try to increase the resolution and brightness of imaging systems to provide better picture quality, but also face constraints associated with providing such increased resolution and brightness.
For example, to increase brightness in imaging display systems, coherent light sources (lasers as one example) have been introduced in the place of incoherent light sources (light-emitting-diodes (LEDs) and lamps, as an example). However, while coherent light sources may increase the brightness of the display system, such light sources often produce images having a noticeable granularity. This grainy pattern, also known as speckle or the scintillation effect, arises due to the highly narrowband and polarized nature of the coherent light incident on a diffuse surface. Speckle has been attributed to the fact that coherent light reflected by or through a diffusing produces a complex, random, but stationary diffraction pattern. Specifically, speckle originates when the coherent plane phase front from a laser traverses through a medium with optical path length differences that are less than or equal to the coherence length of the laser. Such path length differences can occur as a result of surface roughness, scratches, digs, and polishing imperfections in optical elements.
Generally, two different types of speckle exist, namely objective speckle and subjective speckle. Objective speckle arises from the uneven illumination of the object. An object in this scenario may be a Spatial Light Modulator (SLM) such as a Digital Micromirror Device (DMD). When objective speckle exists, even the most perfect optical system can do no better than to reproduce it exactly. On the other hand, subjective speckle arises in the case of an evenly illuminated rough object. Objective speckle exists for almost any light source, while subjective speckle, although it can be present for any source, is worse for a narrowband and polarized source (e.g., a laser).
Accordingly, what is needed is a method and system configured to reduce speckle.